Our studies in this project to date have demonstrated the ability of blood monocytes to carry our direct cytotoxicity to tumor cell kines and ADCC to both red cell and tumor cell targets. Monocytes from patients with cancer were found to have normal levels of monocyte cytotoxicity and serum from cancer patients did not have inhibitors of monocyte cytotoxicity to tumor cells. Preliminary studies indicate that interferon can activate human monocyte direct tumor cell cytotoxicity and ADCC in vitro. We have also demonstrated in an animal model that MVE-2, an interferon inducer, can cause activation of monocyte and alveolar macrophage ADCC in vivo. We propose to characterize the in vitro effects of various types of interferon on monocyte direct cytotoxicity and ADCC as well as lymphocyte ADCC and NK activity. We will also determine the responsiveness of cancer patients' monocytes and lymphocytes to interferon effects in vitro. In vivo effects of chemically defined immune stimulants on rabbit monocyte and alveolar macrophage ADCC will be examined. These studies should provide new insights into the effects of various interferons on monocyte and lymphocyte cytotoxic mechanisms and to examine the effects of immune stimulants (some of which induce interferon) on rabbit monocyte and macrophage cytotoxic mechanisms.